1. Field of the Invention
The present invention relates to a color image forming apparatus having a plurality of photoconductive members wherein each of plural latent images is formed on a surface of a separate photoconductive member and is developed by utilizing liquid development for each of the color images.
2. Description of the Related Art
In a conventional color image forming apparatus, it is known that each latent image, which is developed by utilizing dry developer or liquid developer, is formed on the surface of a separate photoconductive member in accordance with information of each color resolution. The developed images are transferred onto a transfer sheet and fixed by a pair of fixing rollers. Toner for liquid development (WET-TYPE) has an advantage of producing a high quality copied image, since toner particles for liquid development are much smaller than those for dry development and since toner for liquid development has excellent transparency characteristics and produces fine image resolution. However, the liquid development, which has different characteristics than does dry developer, is difficult to use due to its fluidity, viscosity, etc., and such a color image forming apparatus using a plurality of color developers has many difficult problems.
An example of a color development system wherein a plurality of developing units are disposed below a drum type photoconductive member and the developing units are moved for developing each color image on the photoconductive member corresponding to each color resolution is disclosed in Japanese Laid-Open Publication No. 55-12758. In addition, in another example of a color development system, a color image forming apparatus uses a four color developer (yellow, cyan, magenta and black) having two developing units, wherein two color images are developed by each unit. Moreover, while one developing unit develops one color image, the developer in another developing unit is exchanged and the developing unit is cleaned. This is disclosed in Japanese Laid-Open Publication No. 3-186870.
In the prior art disclosed in Japanese Laid-Open Publication No. 55-127580, the liquid developer is liable to adhere to the photoconductive member portion where the liquid developer is not necessary, due to its fluidity and viscosity. This contaminates a transfer portion so that after transferring, the liquid developer gets mixed with other developer in the developing units disposed below the drum type photoconductive member. Such mixing causes a color mixture problem.
In order to prevent such problems, there is required an extra device or a complex structure, such as a device for preventing the liquid developer adhering to the photoconductive member portion where a developer is not necessary, a device for removal of the developer for cleaning or a device for reusing the developer for cleaning. The extra device or the complex structure increases the cost of the apparatus.
In the prior art disclosed in Japanese Laid-Open Publication No. 3-186870, it is difficult to avoid the color mixture problem and there is a limitation of image forming speed because two color images are developed by one developer unit.